"Long before it's in the papers"
May 31, 2011

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Mammoths weren’t picky, happy to interbreed, scientists say

May 31, 2011
Courtesy of McMaster University 
and World Science staff

The woolly mam­moth may have often mat­ed with a very dif­fer­ent, much larg­er type of mam­moth, bio­lo­gists say.

The woolly, which roamed the cold Arc­tic tun­dra, in­ter­bred with the Co­lum­bi­an mam­moth, which pre­ferred the milder re­gions of North Amer­i­ca and was some 25 per­cent larg­er, the re­search found.

“There is a real fascina­t­ion with the his­to­ry of mam­moths, and this anal­y­sis helps to con­tex­tu­al­ its ev­o­lu­tion, migra­t­ion and ecol­o­gy,” said bi­ol­o­gist Hen­drik Poinar of Mc­Mas­ter Un­ivers­ity in Can­a­da. Poinar and col­leagues se­quenced the so-called mi­to­chon­d­rial ge­nome of two Co­lum­bi­an mam­moths, one found in the Hun­ting­ton Res­er­voir in Utah, the oth­er near Raw­lins, Wy­o­ming. They com­pared these to the equiv­a­lent da­ta from a na­tive North Amer­i­can woolly mam­moth.

A mi­to­chon­drial ge­nome is the set of genes found in the mi­to­chon­dria, small cel­lu­lar power-producing sta­t­ions. These genes are un­iquely suit­ed to re­veal­ing an or­gan­is­m’s moth­er-line an­ces­try be­cause they are passed down from the moth­er.

The in­ter­breed­ing an­i­mals were “very phys­ic­ally dif­fer­ent,” said Poinar, whose team’s find­ings ap­pear in the re­search jour­nal Ge­nome Bi­ol­o­gy. “When gla­cial times got nas­ty, it was likely that wool­lies moved to more pleas­ant con­di­tions of the south, where they came in­to con­tact with the Co­lum­bi­ans at some point in their ev­o­lu­tion­ary his­to­ry. You have roughly one mil­lion years of separa­t­ion be­tween the two, with the Co­lum­bi­an mam­moth likely de­rived from an early migra­t­ion in­to North Amer­i­can ap­prox­i­mately 1.5 mil­lion years ago, and their woolly coun­ter­parts em­i­grat­ing to North Amer­i­ca some 400,000 years ago.”

“We think we may be look­ing at a ge­net­ic hy­brid,” said Ja­cob Enk, a grad­u­ate stu­dent in the Mc­Mas­ter An­cient DNA Cen­tre. “Liv­ing Af­ri­can el­e­phant spe­cies hy­brid­ize where their ranges over­lap, with the big­ger spe­cies out-competing the smaller for mates. This re­sults in mi­to­chon­d­rial ge­nomes from the smaller spe­cies show­ing up in popula­t­ions of the larg­er. Since wool­lies and Co­lum­bi­ans over­lapped in time and space, it’s not un­likely that they en­gaged in si­m­i­lar be­havior.”

The sam­ples used for the anal­y­ses date back an estimat­ed 12,000 years. Mam­moths be­came mostly ex­tinct by about 10,000 years.

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A DNA study sheds new light on the complex history of the woolly mammoth, suggesting it mated with a very different, much larger relative, scientists say. The woolly mammoth, which roamed the cold Arctic tundra, interbred with the Columbian mammoth, which preferred the milder regions of North America and was some 25 percent larger, the research found. “There is a real fascination with the history of mammoths, and this analysis helps to contextualize its evolution, migration and ecology,” said biologist Hendrik Poinar at McMaster University in Canada. Poinar and colleagues sequenced the so-called mitochondrial genome of two Columbian mammoths, one found in the Huntington Reservoir in Utah, the other near Rawlins, Wyoming. They compared these to the equivalent data from a native North American woolly mammoth. A mitochondrial genome is the set of genes found in the mitochondria, small cellular power-producing stations. These genes are uniquely suited to revealing an organism’s mother-line ancestry because they are passed down from the mother. The interbreeding animals were “very physically different,” said Poinar, whose team’s findings appear in the research journal Genome Biology. “When glacial times got nasty, it was likely that woollies moved to more pleasant conditions of the south, where they came into contact with the Columbians at some point in their evolutionary history. You have roughly one million years of separation between the two, with the Columbian mammoth likely derived from an early migration into North American approximately 1.5-million years ago, and their woolly counterparts emigrating to North America some 400,000 years ago.” “We think we may be looking at a genetic hybrid,” said Jacob Enk, a graduate student in the McMaster Ancient DNA Centre. “Living African elephant species hybridize where their ranges overlap, with the bigger species out-competing the smaller for mates. This results in mitochondrial genomes from the smaller species showing up in populations of the larger. Since woollies and Columbians overlapped in time and space, it’s not unlikely that they engaged in similar behaviour.” The samples used for the analyses date back an estimated 12,000 years. All mammoths became extinct about 10,000 years ago except for small isolated populations on islands off the coast of Siberia and Alaska, according to scientists.